New Top One dimensions for Homer

[Marconi]

i would like your opinion on the performance locally on the NTO verses the old astroplane

Hotrod, I'm waiting on some signal reports from Homer too, but I'm not sure he still has an Old Top One or an original AstroPlane. He might have some notes though.

Here is a link to a signal report video I took during some testing I did in the spring of 2011. I used SSB, so it's a bit harder to determine signals when the signals are close, but maybe you can get some idea from what I experienced with a new Sirio Top One vs. and Old Top One that Copper's use to sell. I don't see a big difference except in RX is better with the NTO.

The old model that looked much like the original also had a full 1/4 wave radiator about 87.5" - 88.5" in the top.

The main thing I noticed in this video is the difference noted in the RX signals and how close the TX signals were with both antennas. But I have to consider that I had my RF gain all the way open too, and I later found out from Bob85, that could account for the similar signals. I also comment in the video about the differences in location effect that might be working with the setup I have here at my base. So, consider these idea in your thinking.

I wish I could do all this stuff over, but it is too late for this old man...that is why I go by Grandpa on the radio and in my videos.

Marconi's New Top One vs. Old Top One with full 1/4 wave radiator #2 - YouTube

 

[HomerBB]

I did not respond to your post above because it confused me. When I read it I was curious why you had the notion to isolated the radials if you were using a gamma.

As I explained above, I had just started out doing what I always do on vertical GPs, which this resembles at a glance.

Didn't you tell us you checked the match with the setup above and you got 1.2:1 SWR?

Yes I did.

I wonder how that setup would work using a gamma and isolating the radials?

That is the way it was when I had a 1.2:1 SWR.

You also noted that you had not yet made a top hat and instead you extended the radiator out to a full 1/4 wavelength at 87.5" in the beginning. Then later you said the radiator was 89.5" inches.

Yes, I was trying to find resonance on 27.385, so I moved it out. X=0 way higher up the band, so an extension of the length was necessary.

My notes indicate that I found 87.5" inches was resonant at 27.205 mhz using the original A/P 47" x 3/4" base radiator and the top element of my Sigma 4 at 45" x 1/2" inches. I would like to confirm my findings if you can help.

When I removed the insulator from between the radials hub and the vertical I immediately ran into trouble with my tune (more on that later).
The resonance at 27.205 may very well be born out in my post further down from here. We'll look at it.

What diameter tubing did you use for your radiator?

Mine is 1-3/8" diameter.

Thanks,

Keep us posted on your progress.

I also talked to some guy in Hawaii on my Starduster yesterday afternoon late.

Sweet!

 

[HomerBB]

i would like your opinion on the performance locally on the NTO verus the old astroplane

Hotrod, I'm waiting on some signal reports from Homer too, but I'm not sure he still has an Old Top One or an original AstroPlane. He might have some notes though.

I will have to work from memory, or if I can find any old postings about it.
Marconi is correct. I no longer have either AP that I had.

 

[HomerBB]

Some construction highlights of the cap hat construction:

Here is the completed Cap Hat, and the readings from the Analyzer before sundown shut me down again:

Here is a very bad photo of the antenna I took as darkness fell. I'll get a good one tomorrow:

When I took the insulator away from the radials I saw the tune fall completely apart. No amount of working with the gamma settings got me anywhere lower than a 1.7:1 SWR.
I figured it might be time to add the Cap Hat and see whether that would get me nearer my goal. No joy. Just the same everywhere on the band.
However we were resonant as indicated by X=0

I was attempting to reuse the gamma I had made for the Vector 4000. I was getting no where fast. Next I put together another gamma. For it I used a 1/2" diameter tube and a 3/8" x 24" rod with vinyl tubing between them. Still I got nothing in return for all my wasted time trying to tune.

I had only a 17" piece of 1/2" aluminum tube left to work with as a new gamma, but decided that I would go ahead. I found more 3/8" rod, but this time it was 36" long. I tried to guess about where to set the strap to the rod and vertical element by looking at the one of two photos I have been able to locate of an NTO by googling it. I put the strap about 5" short of the end of the rod, extended the rod out from the upper end of the gamma tube 26" instead of 27" because the tube was an inch short of the original. This proved to be critical. Clearly the point of contact for the strap, the length of extension and of the rod itself can not be compromised.

This was the last thing I did today as night was falling. I had no time to finely tune the antenna today.

 

[HomerBB]

@Marconi.

About the difference/sameness of the resonance between the Cap Hat version and the extended vertical version, My cap hat can be removed and replaced at will with the extended vertical. I can do this later when I have gotten it tuned and tested with the Cap Hat.
I'd like to see if the gamma settings are the same by simply replacing the CH with a long tube.

Resonance at 27.205 - maybe, it seems right now the nearest I can tell is resonance is low. I'm thinking that once I tune for the resonance with the Cap Hat cahnging to the vertical may very well result in that. We'll see.

 

[HomerBB]

Better photo:

 

[HomerBB]

Since I might be the only one around that will talk to you about the New Top One or the AstroPlane...can I ask some questions?

I meant to reply to this specifically before.
I think that some feel this is an already done subject. That's ok with me. That's why I asked you about the dimensions in a PM. I have the V4k radials standing idle, and I haven't been able to do any antenna projecting due to business and weather, so I figured I'd get a fix with a quick repurpose of the radials. I realize I had made an assumption ortwo that has made this once again a little more interesting.

1. I was obviously looking at it as a simple 1/4GP which triggered me to isolate the radials.

2. It may be a simple 1/2 wave vertical dipole with a shortened capped end and a widened end that works to greatly broadband it. I don't know, but there seems to be room for discussion, of just fun. . .

3. The antenna is not as forgiving as a simple 1/4GP. As it was/is with the V4k, I have learned the gamma dimensions and tap points on the rod and vertical are not optional. The broadbanded nature of the antenna belies the exactitude of its components. As a 1/4 wave GP will work most anywhere in the ballpark of dimensions, this one will not.

This is turning into more fun than I had anticipated.

 

[HomerBB]

A friend came by after work today for a visit. He took my homebrew Astroplane with him. However, that left me with limited time to attempt to tune the NTO without the Cap Hat. I felt I had gotten to resonance with the length adjusted to 89.5" from the radials hub upward.

I read through this again and believe it is confusing and unintentionally misleading. The above portion of the post is an action I took to put the radials back to grounding to the vertical. The SWR went way up when I did this.

I began to try to draw the SWR/tune down from 1.2:1 when the jumper I was using decided to ground out on me. I need to make a brand new one. I'll have to get back to it later. The SWR in the shack is flat on 27.385, but we shall see what it looks like with the analyzer after the weather clears back up . . .

This SWR was where I had been before I grounded the radials to the vertical. With the lowest SWR using the original gamma at its lowest of 1.7:1, it was usable for short transmissions, but clearly not where I needed it. I thought my e1/ƛ jumper was bad at the time I wrote this. I made a new one and the result with the higher SWR was the same. Both jumpers are good. I would need a gamma that was closer to the NTO makers dimensions.

 

[Marconi]

@Marconi.

About the difference/sameness of the resonance between the Cap Hat version and the extended vertical version, My cap hat can be removed and replaced at will with the extended vertical. I can do this later when I have gotten it tuned and tested with the Cap Hat.

I'd like to see if the gamma settings are the same by simply replacing the CH with a long tube.


Resonance at 27.205 - maybe, it seems right now the nearest I can tell is resonance is low. I'm thinking that once I tune for the resonance with the Cap Hat cahnging to the vertical may very well result in that.

We'll see.

When you make the change with the top hat I would expect the match to be very close if the length is close. Otherwise, I don't see how there could be much of a difference. As best I can recall when I made the change on my Old Top One the first two tries I made the length too short and then too long. I can recall all I had to do was get the length right and I got the resonace right on with the third try however I was using a working feed line.

When I requested your confirmation of my full 1/4 wave length at 27.205 resonance I was not sure what you used for the diameter of tubing in your NTO.

My testing idea for the full 1/4 wave used the old top one with a much smaller radiator diameter, so I don't think we can expect to prove much as a result of comparing.

I don't know how much difference such a diameter difference would make, but under the circumstances I would expect your NTO to be too long if you used the length I found at about 87.5" - 89.5" inches while using .625" average radiator diameter.

I meant to reply to this specifically before.
I think that some feel this is an already done subject. That's ok with me. That's why I asked you about the dimensions in a PM. I have the V4k radials standing idle, and I haven't been able to do any antenna projecting due to business and weather, so I figured I'd get a fix with a quick repurpose of the radials. I realize I had made an assumption ortwo that has made this once again a little more interesting.

1. I was obviously looking at it as a simple 1/4GP which triggered me to isolate the radials.

2. It may be a simple 1/2 wave vertical dipole with a shortened capped end and a widened end that works to greatly broadband it. I don't know, but there seems to be room for discussion, of just fun. . .

3. The antenna is not as forgiving as a simple 1/4GP. As it was/is with the V4k, I have learned the gamma dimensions and tap points on the rod and vertical are not optional. The broadbanded nature of the antenna belies the exactitude of its components. As a 1/4 wave GP will work most anywhere in the ballpark of dimensions, this one will not.

This is turning into more fun than I had anticipated.

#2. I'm not sure, but you might be right about the radial cone being much larger and making the bandwidth wider. Since you got a good SWR with the radials isolated...maybe the mast was serving as the bottom of the dipole instead of the radials if you didn't have your mast isolated.

My New Top One shows a nice wide bandwidth of over 4.4:1 using my analyzer at the radio end of the feed line, and about 5.4:1 with my inline meter, so I think the results I would actually get at the feed point would be somewhat less. Sirio publishes a 2.0 mhz bandwidth range of <1.50:1, so I'm not sure what exactly causes your antenna to show 7.40 mhz for <2.0:1.

I gave you the gamma dimensions I have, but I can't suggest any solution to your matching issue. I will say that the top of the NTO does have a hub that supports the top hat radials and it is at least 2" or more tall, so the gamma strap does mount a little below the very tip like you found.

The last few days have been tough for me Homer, so I hope I am making sense in my posting to your comments.

 

[M0GVZ]

Question: Something puzzles me and that is how can X=0 over such a wide range? According to those analyser pictures the antenna is resonant over 5Mhz? Sure low SWR over such a bandwidth isn't uncommon but no reactance over 5MHz? Or is it just resonant at those points?

Just trying to understand how the antenna is working.

 

[Captain Kilowatt]

Some construction highlights of the cap hat construction:

I have a question about those meter readings. On 30.318 MHz it seems correct. If R=86 and X=0 then the SWR should be about 1.5:1 OK fine. Now look at 27.099 MHz. It shows R=38 X=0 and the SWR = 1.0:1. How can it show a perfect match when the impedance ratio is of the order of 1.5:1? Same thing for 27.558 MHz.The SWR should be higher. Some of the readings seem correct while some seem off. Can't be bothered to do the math on it right now.

 

[HomerBB]

That is one of the reasons I put the readings up. I'm puzzled too. I have never had this happen with any antenna before using this analyzer.
I was rushed with daylight ending. I'll have to go back to it more meticulously again.

 

[The DB]

I thought the readings looked odd when I saw them but didn't have time to look at them more closely. This morning I plotted the MFJ data on a Smith Chart and got the following expected SWR values:

R=24, X=2, mySWR=2.0, yourSWR=2.0
R=26, X=0, mySWR=2.2, yourSWR=1.5
R=40, X=0, mySWR=1.25, yourSWR=1.1
R=38, X=0, mySWR=1.6, yourSWR=1.0
R=35, X=0, mySWR=1.45, yourSWR=1.51
R=86, X=0, mySWR=1.72, yourSWR=1.5
R=55, X=18, mySWR=1.4, yourSWR=2.0

In one case our SWR figures match, in two cases you have a higher SWR and in four cases you have a lower SWR.

I hope this data helps you sort out whatever it is that is causing your problem.


The DB

 

[HomerBB]

hopefully, it isn't my analyzer on the blink . . .

 

[Captain Kilowatt]

I thought the readings looked odd when I saw them but didn't have time to look at them more closely. This morning I plotted the MFJ data on a Smith Chart and got the following expected SWR values:

R=24, X=2, mySWR=2.0, yourSWR=2.0
R=26, X=0, mySWR=2.2, yourSWR=1.5
R=40, X=0, mySWR=1.25, yourSWR=1.1
R=38, X=0, mySWR=1.6, yourSWR=1.0
R=35, X=0, mySWR=1.45, yourSWR=1.51
R=86, X=0, mySWR=1.72, yourSWR=1.5
R=55, X=18, mySWR=1.4, yourSWR=2.0

In one case our SWR figures match, in two cases you have a higher SWR and in four cases you have a lower SWR.

I hope this data helps you sort out whatever it is that is causing your problem.


The DB

Pretty much what I had figured on as well.